Implement `NetworkService`'s `handle()`-methods

### Problem

We need handle()-methods:

- [x] NetworkUncheckedSubmit.handle()

### Solution

Implement the above

### Alternatives

_No response_

Start by locating NetworkService and its handle() methods, then verify whether NetworkUncheckedSubmit.handle() is already implemented as the checklist indicates. Identify which handle methods remain in scope and confirm that all methods named by the issue are implemented before considering the task done.

Written by the indexing model from the issue text.